Semi-conductor devices are often used in oscillators for generating clock signals, so as to control the operation of electric devices. In order to let the oscillator circuit function properly, the frequency of the clock signal generated by the oscillator circuit is set within a predetermined range even with an expected temperature change. Generally speaking, for stabilizing the operation of an electric device, it is usually required to reduce the temperature efficiency with respect to the frequency and the period of an oscillator.
However, in a low power operation mode, with a low voltage, it is difficult to compensate for the temperature efficiency. From the opposite point of view, how to apply the temperature efficiency becomes another choice that is worth discussing.